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<br />Examination of the profile indicated by the survey shows widely varying slopes <br />between adjacent cross-sections. The reach-length weighted average slope for the problem area <br />is 0.00097, but the individual values range from a relatively steep 0.00476 to an adverse - <br />0.00l40. More disturbingly, the values change sign quite often, with six consecutive cross- <br />sections being the longest stretch of positive slope within the model, and two to three se:ctions <br />being typical. Tellingly, the portion with the most frequent directional changes in slope:, i.e., <br />positive to negative or vice versa, coincides with an area heavily encroached upon by <br />agriculture. Aerial photography indicates numerous old river scrolls within the cropland, and <br />shows a large meander bend truncated by encroachment. At the upstream end of this be:nd the <br />river is oversteep and then bounces frequently between positive and adverse slopes to near the <br />bottom of the reach. It is probable that the encroachment is most responsible for the radically <br />varying slope. This likely occurred as a combination of the actual excavation (and probable <br />over-excavation) performed to move the river channel from the potential agricultural land and <br />the river's adjustment to the imposed disequilibrium of unstable channel and planform <br />geometry. A profile plot of this area is shown in Plate 2. <br /> <br />Problem Area 4 is suspected to be aggrading, although this can not be stated with <br />certainty at this point. This is consistent with the apparent downstream movement of an. <br />aggradational trend observed in the degradation rangelines. <br /> <br />The "JR2" particle size distribution was used for this sub-reach for sediment transport <br />calculations. The sediment yield for this problem area under existing conditions was 5,600 <br />tonslyr with a mean daily load of 15 tons/day. <br /> <br />Problem Area 5. Hydraulic modeling of Problem Area 5 indicated that the capacity <br />within tl1e active channel banks is approximately l,500 cfs. This is the value above which flow <br />begins to significantly inundate the overbank areas adjacent to the river channel. Only one <br />cross-section (out of 75) within the model indicates flows in excess of 4,000 cfs could cause <br />damage to the adjacent agricultural area though, again, much of the flow area for lesser flows is <br />outside the channel proper. The next potentially damaging flow occurs at approximately 6,000 <br />cfs, with a substantial portion of the model sections indicating potential damage at flows above <br />this amount. The 3,000 cfs operational discharge was modeled to indicate potential problem <br />areas under current conditions. The flow area extents for this discharge were not plotted for <br />this area, since it did not indicate potential surface water damages. The area with its cross- <br />sections is shown on Sheet 3. <br /> <br />Examination of the profile indicated by the survey shows varying slopes between <br />adjacent cross-sections, though not to the degree of area 4. The reach-length weighted average <br />slope for the problem area is 0.00 ll8, but the individual values range from a relatively steep <br />0.00742 to an adverse -0.00059. This steep slope is associated with an irrigation diversion <br />within the reach. Another steep value of 0.00682 along with an adverse value of -0.00032 <br />occurs just upstream of a bridge crossing and is the result of the flow constriction there. The <br />steepest value not related to a known structure is 0.00421, but is again associated with human <br />activities. This value occurs where a meander loop has been cut-off by mechanical means. <br />The adverse slopes are infrequent and not alarming for a natural channel. Compared to other <br /> <br />20 <br />